This invention relates to a pneumatic control apparatus for bi-manual security of the type comprising an OR cell, connected, at the input side, to two supply conduit lines, and, at the output side, to a capacitor, through a debit regulator, and AND cell, connected, at the input side, to the two supply conduit lines, a so-called prioritary cell, comprising a valve member, arranged for engaging a first seat, under the action of the pressure inside the capacitor, and a second seat, under the action of the output pressure of the AND cell in an input conduit of the prioritary cell, an output conduit which can communicate with the input conduit through the first seat, the prioritary cell being arranged so that the communication between its input and output conduits remains cut off after the pressure appears again in one of the two supply conduits in which the pressure dropped before.
Such a pneumatic control apparatus for bi-manual security is described, for instance, in French Pat. No. 72 16898. The object of this apparatus is to improve the security in connection with the control of machines which are dangerous for the hands of operators, such as presses.
Nevertheless, such an apparatus has the drawback that the bi-manual security is not guaranteed anylonger, when the two supply pressures are not equal.